RICHARD A. YETTER is Professor of Mechanical Engineering at the Pennsylvania StateUniversity. He received his B.S. from Syracuse University, M.S. from Cornell University,and M.A. and Ph.D. from Princeton University. His current research interests includepropellant and nano energetic materials combustion, high temperature / high-pressure combustion chemistry, heterogeneous combustion, and micro propulsionand power systems.

He was previously a Research Engineer at the Scientific Research Laboratories ofFord Motor Company, a Senior Research Scientist and Lecturer at Princeton University,and a Research Collaborator at the Brookhaven National Laboratory.

He is an editor of Combustion Science and Technology, co-editor of the 30th and31st Proceedings of the Combustion Institute, associate editor of International Journalof Energetic Materials and Chemical Propulsion, section editor of Frontiers of Energyand Power Engineering in China, and currently serves on the editorial board ofProgress in Energy and Combustion Science and Journal of Propulsion and Power.

Dr Yetter is an author or co-author of over two hundred scientific publications,two books, and two US patents. He is the recipient of the Silver Medal andDistinguished Paper Awards from the Combustion Institute, and the MartinSummerfield Best Paper Award and Best Poster Paper Award from the Sixth and EighthInternational Symposium on Special Topics in Chemical Propulsion, respectively.

Nanopropellants• Energy density vs. sensitivity.

• Nanopropellants will not necessary provide higherenergy densities, but can provide improved usage of thestored chemical energy. Nanoingredients could producenew gelled and solid propellants. Nanopropellants maybe used in non-conventional applications.

• NASA Nanotechnology Roadmap: “Passivationchemistries must be developed to prevent prematureoxidation of the nanoparticles and synthesis methods,including self-assembly based techniques, are neededto tailor the shape and size of the nanoparticles in orderto control burn rates.”

• Self-assembly and supramolecular chemistry of the fuel and oxidizer elements of energetic materials have lagged far behind chemistries in other disciplines (such as pharmaceuticals, microelectronics, microbiology).

• There is limited fundamental understanding of what type of supramolecular structures provide desirable performance in combustion, mechanical, and hazard characteristics.

Critical Technology Issues

Structure of the Abalone Shell

A. Lin and A. Meyers, Mat. Sci. Eng. A 390, 27-41, 2005.

inorganic layers: CaCO3 - aragonite

organic layers:

Structure of the nacre:95 wt.% inorganic material5 wt.% organic material

Nanoparticle Self-Assembly

Sanders, J. V., Murray, M. J., Naturev275, 1978.

Shevchenko, E. V., Talapin, D. V., Kotov, N. A., O’Brien, S., Murray, C. B., Nature v439, 2006

Kalsin, A. M., Fialkowski, M., Paszewski, M., Smoukov, S. K., Bishop, K. J., Grzybowski, B. A., Science v312, 2006

Organization and Assembly at the Nanoscale

Surface Passivation of Bare Al Nanoparticles Using Perfluoroalkyl Carboxylic Acids (C13F27COOH)

100 nm

SEM (225 000 magnification) of Al-C13F27COOH

R.J. Jouet, A.D. Warren, D.M. Rosenberg, V.J. Bellitto, K. Park, and M.R. Zachariah, Chem. Mater. 17 (2005) 2987-2996.R.J. Jouet, J.R. Carney, R.H. Granholm, Sandusky, H.W. and A.D. Warren, Mater. Sci. Technol. 22 (2006) 422-429.

FTIR Spectrum

C=O

O-H

Self-Assembled Nanoscale Thermite Microspheres

~4 μm

60nm 100nm

nAl (38nm) nCuO(33nm)

nAl-TMA(trimethyl(11-mercaptoundecyl)ammonium chloride

nCuO-MUA(11-mercaptoundecanoic acid )

•Create Self-Assembled Monolayer (SAM) on surface of individual particles

•Monolayers contain a functionalized group at tail end (either + or – charged)

•When mixed in a diluted and slightly elevated temperature they form macroscale structures with nanoscale constituents

Kalsin et al., Science, v312, 2006

Malchi, J., Foley, T., Yetter, R.A., ACS APPLIED MATERIALS & INTERFACES, 1, 11, 2420, 2009

Functionalized Graphene Sheets as Catalysts Supportsfor Liquid Propulsion

• FGS active sites: – defects as radical sites– carboxylate (edge), epoxide

and hydroxyl (surface) functionalities

– The C/O ratio is adjustable from 2 to 500, i.e., FGS2 to FGS500

H.C. Schniepp, et al., J. Phys. Chem. B (2006)

J. L. Sabourin, D. M. Dabbs, R. A. Yetter, F. L. Dryer, and I. A. Aksay, ACS Nano, 3,12,3945,2009.

Burning Rates of CH3NO2 Enhanced

a: epoxide on graphene, b: hydroxide on graphenec, d: in-plane and overhead view of a FGS

Nanoengineered Energetic Materials

• At the microscale: nanoenergetics on a chip

• Heat, pressure, specific gases on demand => propulsion, power, actuation, instrument calibration, pumping, switches, initiators

• Conventional MEMs fabrication methodology: soft lithography, screen and inkjet printing, PVD, etc.

• New fuels and oxidizers: porous silicon, nanothermites, and intermetallics

• Scale-up to the macroscale

Zhang, et al, Nanotechnology 18 (2007)Zhang, et al, J. of Micro ElectroMechanical Systems, 2008

~1W ignition power, 0.1 ms ignition delay, 0.12 mJ ignition energy60 mJ output energy

Micro initiator/ Micodetonator CuO/Al nanothermite on igniter chip (1mm²)

Ignition of a propellant has been demonstrated

1 cm3 MEMS Safe Arm FireMEMS integrate sensors, circuitry, actuator, electrical protections (pyrotechnical switches), highly energetic material ([Co(NH3)6]2[Mn(NO3)4]3 , Al/CuO nanothermite), moving barrier….

Gas generator EM thin layerChip size 1cm²

IntegratedNanothermite

MEMS Device Integrating Nanothermite Al/CuO

Au/Pt/Cr thin film heater

Patterned SiO2 & Cu films

CuO nano wiresAl/CuO nEM

Pezous et alJ. Phys & Chem. Solids 71, (2010)Pezouset al, Sensors and ActuatorsA159, 2010

PSi as a Nanostructured Fuel

Cross-section SEM image of PSietched 60mA/cm2 at x35k magnification (Parimi, S.V., Tadigadapa, S. Yetter, R.A.

NaClO4 x 1H2O loaded PSi burn (Son, SF)

Surfaces prepared through white light promoted hydrosilyation on pSi(Stewart, MP, and Buriak, JM, J. Am. Chem. Soc. 2001, 123, 7821). Thermally induced hydrosilylation with perfluoro-1-octene and perfluoro-1decene (Son, SF)

nSi/nCuO propagation rates; PVD of CuO on pSi, Gesner, J. and Yetter, RA

Churaman et al., Chem. Phys. Letts. 464, 198, 2008 .

• McCord et al observed fast combustion reaction of PSi with nitric acid (1992)

• Explosive oxidation of PSi in liquid oxygen by Kovalev et al (2001)• Composite solid state system based on PSi pores filled with gadolinium

nitrate at room temperature by Mikulec et al. (2002)• Clement et al (2004) and du Plessis (2006) study various oxidizers and

begin construction of MEMs devices• Examples of pore fillers: NaClO4 x 1H2O, Ca(ClO4)2 x 4H2O,

Magnesium Perchlorate, Sulfur, PFPE

Light-Activated Ignition of Si Nanowires

N. Wang,* B. D. Yao, Y. F. Chan, and X. Y. Zhang, Nano Letters, 2003, 3, 475n

Packaged nanoporous silicon energetic devices

Functionalization of Si Surfaces

Psi-oxidizer energetic materials

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14 16 18 20 22 24 26 28 30

% Silicon

13

• Bi-modal propulsion system with single propellant => chemical micro-propulsion and MEMs electro-spray, micro resistojets

Integrated solid oxide fuel cell / microthruster

electrolyte

H2

Partially decomposed monopropellant or NxOy

+

H2/H2O

anode

cathode

i

e-

High T Fuel Cell

• Propulsion system as an electric power source

•Propulsion system as a satellite structural component (self-consuming satellites) => improved spacecraft mass ratio

Single propellant

tank

Electric power

Completely decomposed fuel-rich propellant

Multifunctional Micropropulsion

MEMS-based Pyrotechnical MicrothrustersLAAS-CNRS

3.3

2.8

2.3

1.6

1.3

0.8

0.3

-0.2300 500 700 900

Thrust profile with a throat dia. of 500 m

Time (ms)

Thru

st (

mN

)

ZPP Igniter peaks Flame passes through

intermediary chamber

GAP/AP combustion in chamber

• 100 addressable microthrusters with 3 main micromachined layers

• Combustion chamber 1.5 x 1.5 x 1 mm• glycidyle azide polymer (GAP) mixed with AP

and Zr particles propellant• zirconium perchlorate potassium primer

• Polysilicon resistor igniter at nozzle • Insulating groves to eliminate cross-talk• Main grain was screen printed under

vacuum• 100% ignition success with 250 mW• Thrusts ~0.3-2.3 mN

Rossi et al., Sensors and Actuators A, 121, 508-514, 2005, Sensors and Actuators A, 126, 241-252, 2006. Journal of MEMs, 15, 6, 1805-1815, 2006.

Micropropulsion system as an electric power source

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P - NO2 400SCCM

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• Direct Flame Solid Oxide Fuel Cells (DF-SOFC) provide one approach for incorporating power generation within the thruster combustion chamber.

• Ideal for incorporation into LTCC and HTCC combustors.• Partially decompose liquid monopropellant to achieve NxOy gases for selective

cathode. • Completely oxidized liquid monopropellant for hydrogen rich gases to anode.• Successful operation with partially decomposed HAN-based monopropellant.

Solid Electrolyte: Yttria-Stabilized Zirconia; Anode: metallic Ni; Cathode: Strontium-Doped Lanthanum Manganite

Polarization curves Polarization curves

• Benefit– May enable new missions; improvements in performance (15-40% =

likely: factor of 2+ = risky)

• Alignment with NASA Needs– Low cost to space, long term storage of propellants in space, robotic

sample return, sounding rockets, scramjets, upper stage engines, booster stages, launch abort stages, nano and pico satellites

• Alignment with non-NASA aerospace technology needs– Direct synergy with DoD in the areas of propulsion and energetic

materials.

• Alignment with non-aerospace national goals– Possible impact on alternate fuels and emissions, nanoenergetics on

chips for power generation, actuation, micro welding and fusing, long term energy storage shelf life, etc. [pressure (kPa-GPa), heat (200-3000oC), chemical species (neutral and ionized gas)]

• Technology risk and reasonableness– For development of new energetic materials (i.e., synthesis of new

molecules-risk is extremely high); for development of new passivationand assembly methodologies- risk is high, for inclusion of nanomaterialsin energetic materials – risk is low to moderate)

• What are the top technical challenges in the area of your presentation topic?– Particle passivation and assembly– Scale-up of materials and manufacturing– System implementation (e.g., for metalized gels,

pumping and injection) – Replacements for cryogenic hydrogen

• What are technology gaps that the roadmap did not cover?– Integration of nanoenergetics with sensors,

electronics, etc.– Graphene as a fuel, catalyst, high energy material,

e.g., with polymeric nitrogen– Health and handling issues

• What are some of the high priority technology areas that NASA should take?– Passivation of nano aluminum with reactive

component and assembly to the micron scale.

– Gelled hydrogen.

– Application of nanoenergetics beyond propulsion.

• Do the high priority areas align well with the NASA’s expertise, capabilities, facilities and the nature of the NASA’s role in developing the specified technology? – Yes

• In your opinion how well is NASA’s proposed technology development effort competitively placed? Nanomaterials for propulsion important to both propellants and propulsion systems;Nanoengineered energetic materials also of importance and under study by DoD and DOE

• What specific technology can we call as a “Game Changing Technology”? Achieve performance of cryogenic hydrogen and oxygen with non-cyrogenic propellants or exceed cyrogenichydrogen with nano ingredients. Other measures may produce game changing technology as well, such as cost.

• In your opinion what is the time horizon for technology to be ready for insertion (5-30yr)?

– 5-10 years for inclusion of nanomaterials as gelling agents or ingredients in solid propellants

– 5-10 years for organized assembly of nanoenergetics on chip-sized devices

– 10+ years for organized assembly of macroscalepropellant grains

Motivation

• Cyro-propellant performance without cryo shortcomings

• Nanotechnology for designing and assembling future propellants

• Multi-functionality for both propulsion and power applications

0.1

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Bu

rnin

g R

ate

[cm

/s]

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rb [cm/s] = 4.5*(P[MPa])

0.47

ADN* CL-20*

HNF*

JA2#

HMX** Altwood, 1999# Kopicz, 1997

Nano-Aluminum/Ice Propellants for Replacement of Cryogenic Hydrogen

Burning rates of 38 nAl & liq. H2O

1.5” dia. x 1.5” long center perforated 80nAl-ice grain

Research• nAl-H2O composites are studied as a means to generate hydrogen at high

temperatures and at fast rates• Composites have high energy density and low sensitivity• Combustion occurs without heat releasing gas phase reactions & thus many

flame spreading and instability problems of conventional propellants are eliminated.

nAl-ice grain in phenolic tube

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= 1.0

Risha, G.A., Son, S.F., Yang, V., & Yetter, R.A., 2008

Efficiency of H2

production

2Al + 3H2O → Al2O3 + 3H2